GIRARD — Teachers at North Mac Middle School in Girard were told not to issue hall passes to students during classes this week after graffiti that included threatening language was found Monday in a bathroom, School Superintendent Marica Cullen said Thursday.

Cullen said she personally searched lockers at the school after the graffiti was found, and the district determined by 3 p.m. Monday that there was no credible threat of violence.

The graffiti, which also included “anatomical” images and sexually suggestive messages aimed at administrators, is being treated as an incident of vandalism, Cullen said.

“These were kids writing things on walls that they shouldn’t have been,” she said.

However, the district immediately called police to the school as a precaution.

“We erred on the side of caution,” Cullen said.

Using security camera footage, the school has identified two students believed to be responsible for the vandalism, she said.

“We know who went in, but we don’t know who had pencil and pen in hand,” Cullen said.

No notification went out to parents via the district’s telephone alert system because the school was not placed on a “hard lockdown,” she said. That would involve students being kept in their classrooms and not being allowed to move from class to class.

The school already has started easing the restrictions on passes, but the “soft lockdown” will remain in effect Friday, Cullen said.

Meanwhile, Girard Police Chief Dave Campbell said his officers have stepped up their presence at the school throughout the week.

“With us, it’s taken seriously no matter what,” he said.

The department did not give the district an opinion on whether the graffiti was a credible threat or just an act of vandalism, Campbell said.

Police are attempting to talk to everyone who went in and out of the bathroom where the graffiti was found and are about halfway through those interviews, he said.

The investigation is ongoing, and the department will determine after the school’s winter break whether to continue its heightened presence, Campbell said.